Low-profile transformer and method of manufacturing the transformer

Abstract

A multilayered coil is formed by inserting insulating paper 13 having either a pressure sensitive adhesive or an adhesive disposed on both faces thereof into at least one place between thin coil layers and then magnetic cores 15 are mounted to the multilayered coil from above and below. Thus, a thin transformer for a switching power supply is provided, in which variation in distance between coil 11 and coil 12 , of which one is disposed over the other, variation in distance of coil 11 and coil 12 from magnetic core 15 and the like are suppressed.

1. A thin transformer comprising:
 an insulating paper having one of a pressure sensitive adhesive and an adhesive disposed on both faces thereof;  
 a multilayered coil configured by having said insulating paper inserted into at least one place between thin coil layers; and  
 magnetic cores mounted to said multilayered coil from above and below.  
 
   
   
     2. The thin transformer according to  claim 1 , wherein said insulating paper is a polyimide film. 
   
   
     3. The thin transformer according to  claim 1 , wherein said insulating paper having a pressure sensitive adhesive is a tape having a pressure sensitive adhesive attached thereto. 
   
   
     4. The thin transformer according to  claim 3 , wherein at least one of said insulating papers provided on a bottommost layer and a topmost layer has the pressure sensitive adhesive disposed on both faces thereof. 
   
   
     5. The thin transformer according to  claim 1 , wherein said insulating paper has the adhesive disposed at a portion of the face of said insulating paper. 
   
   
     6. The thin transformer according to  claim 5 , wherein one of the adhesive and the pressure sensitive adhesive disposed on said insulating paper provided on at least one of a bottommost layer and a topmost layer is identical to one of the adhesive and the pressure sensitive adhesive disposed on said insulating paper used between coils. 
   
   
     7. The thin transformer according to  claim 1 , wherein an entire body of said multilayered coil is sealed in an insulating resin. 
   
   
     8. The thin transformer according to  claim 7 , wherein the insulating resin is a thermoplastic resin. 
   
   
     9. The thin transformer according to  claim 8 , wherein the thermoplastic resin is a liquid crystal polymer. 
   
   
     10. The thin transformer according to  claim 1 , wherein at least one of a primary coil and a secondary coil is a coil in a thin plate form. 
   
   
     11. The thin transformer according to  claim 10 , wherein the coil in a thin plate form is a copper plate. 
   
   
     12. The thin transformer according to  claim 1 , wherein at least one of a primary coil and a secondary coil is a coil formed on a printed circuit board. 
   
   
     13. The thin transformer according to  claim 1 , wherein at least one of a primary coil and a secondary coil is a coil formed by winding an electric wire. 
   
   
     14. The thin transformer according to  claim 13 , wherein the electric wire is one of a round electric wire, a flat-rectangular electric wire, and an electric wire provided with a three-layer insulating coating. 
   
   
     15. The thin transformer according to  claim 14 , wherein the electric wire has a solvent bonding layer. 
   
   
     16. The thin transformer according to  claim 15 , wherein the solvent bonding layer is of an alcohol bonding type. 
   
   
     17. The thin transformer according to any of  claims 7  to  13 , wherein a connection portion between said multilayered coil and a terminal is sealed in a resin molding. 
   
   
     18. A method of manufacturing a thin transformer comprising:
 a first step for preparing thin coils constituting primary coils and secondary coils;  
 a second step for forming a multilayered coil by inserting an insulating paper having one of a pressure sensitive adhesive and an adhesive disposed on both faces thereof into at least one place between the thin coils; and  
 a final step for mounting magnetic cores to the multilayered coil from above and below.  
 
   
   
     19. The method of manufacturing a thin transformer according to  claim 18 , wherein, in said second step, the adhesive is applied to a portion of an interface between the insulating paper and the multilayered coil. 
   
   
     20. The method of manufacturing a thin transformer according to one of  claim 18  and  claim 19 , further comprising a step, between said second step and said final step, of sealing up an entire body of the multilayered coil by injection molding. 
   
   
     21. The method of manufacturing a thin transformer according to any of claims  18  and  19 , wherein, in said first step, a coil is formed from a copper plate by punching. 
   
   
     22. The method of manufacturing a thin transformer according to any of claims  18  and  19 , wherein, in said first step, a coil is formed from a copper plate by etching. 
   
   
     23. The method of manufacturing a thin transformer according to any of claims  18  and  19 , wherein, in said first step, a coil is formed by winding an electric wire. 
   
   
     24. The method of manufacturing a thin transformer according to  claim 23 , wherein said first step includes a step of dissolving a solvent bonding layer on a surface of the electric wire with a solvent. 
   
   
     25. The method of manufacturing a thin transformer according to  claim 24 , wherein the solvent is alcohol.